Herbert e



'(No Model.)

H. E. SHREEVE. TELEPHONE TRANSMITTER.

No. 602,174.v Patented Apr. 12,1898.

iZ @f UNITED STATES 'PATENT muon.

HERBERT E. SHREEVE, OFl BOSTON, MASSACHUSETTS, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF SAME PLACE.

TELEPHONIE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 602,174, dated April 12, 1898.

Application led August 26, 1897. Serial No. 649,600. (No model.) v

class of instruments wherein both of the said4 principal electrodes are attached to or mounted on the diaphragm, so as to vibrate therewith.

The invention consists, mainly, in certain` featuresof construction whereby the tendency of the finely-divided conducting material to pack or settle, which presents itself in' all transmitters of this general type,is re-- sisted and largely overcome, and whereby the efficiency of the instrument as a transmitter, whether high or low battery power be employed in association with it, is materially enhanced, so that by the introduction of the said features the operation of inferior forms of transmitter is improved to such an extent that they become substantially as serviceable and efficient as transmitters of the best standard types. v l

In this invention the front and rear ycontact-electrodes are both mounted upon the vibratory diaphragm, the'former rigidly and directly and the latter elastically, and the granular carbon which is lheld between them and in constant contact with both, to constitute the variable-resistance medium, is composed of carbon granules or particles of substantially spherical or rounded form. The contact-electrodes and the interposed spherical granulations of carbon are contained in a case or chamber supported wholly by thediaphragm, and the elastic or resilient attachment of the rear contact-electrode is secured by providing that it shall be formed of or carried by the rear wall of this chamber, which in turn is itself mounted upon the diaphragm by means of an elastic arm or spring-plate. Thus between the rear contact-electrode and the` diaphragm which carries it there is an interposed resilient mechanical connection which constitues also a spring-back for the entire chamber or case.

Figure l of the drawings represents a vertical central section of a transmitter embodying the invention. Fig. 2 is a face view of a spring-disk, which in this instance forms the elastic diaphragm connection of the rear contact-electrode and likewise serves as the front wall of the variable-resistance chamber.

. In the'drawings, F is the face-plate or front of a telephone-transmitter, having a central aperture a, to which is attached a mouthpiece or sound-converging cone M and which widens on the interior surface of the faceplate to form the usual vocalizing chamber Y.

D is the vibratory diaphragm peripherally surrounded by a rubber cushioning-band d and pressed gently toward the face-plate by the dampening-spring cl2, whose end is padded by a sleeve p, of rubber or similar material. C is the case or chamber, which contains the principal or contact electrodes and the finely-dividedresistance-varyingmedium. It consists of a circular box c, of brass or other suitable metal or alloy, having a flange f,'

through which pass threaded holes for the reception of screws and z, whereby it is attached to the plate S, which serves as a front plate to close the chamber.

The plate S is more fully illustrated in Fig. 2, which shows the face it presents toward the diaphragm. In the present instance it is formed as a disk slotted at s and s2, as shown, to render it flexible and to give it resiliency to the end that it may constitute a springback for the case C or an elastic interposed connection between the said case andthe diaphragm, which wholly supports the said case and its contents. The disk is preferably made of vulcanized fiber or similar elastic non-conducting material, but may, if desired, be ofmetal, provided it be formed as or mounted upon a spring or othery elastic connection; but if made ofmetal anon-conducting bushing will be required at its center, through which the front electrode attachment passes. The said front electrode e is a conducting -plate or disk, preferably of carbon, contained in the chamber C, but of course ICO insulated therefrom. It is fastened to a stud or bolt I), which extends through the resilient disk S and the diaphragm, being fitted with a shoulder or washer h between the said disk S and the diaphragm and having on the outside of the said diaphragm anut n, which when screwed down securely attaches the electrode e and the containing-case C to the diaphragm center, the former directly and rigidly and the latter, through the intermediation of the spring-plate S, elastically. The rear or complementary principal or contact electrode e2 is also preferably of carbon and is fastened to the interior back surface of the case C. Thus, while mounted, in common with the front electrode, on the diaphragm, its attachment thereto is elastic because of its being supported by the case C,1whose connection with the said diaphragm is effectuated through the interposed spring-plate S.

The space within the containing-chamber C between the contact-electrodes is filled or nearly filled with a mass of finely-divided and loose granulated carbon g, constituting, in association with the said contact-electrodes, (with which the said mass is constantly in contact,) the variable-resistance medium, and the grains or particles of the said mass are substantially spherical or rounded in form.

It is customary in the art to apply the term electrodes in transmitters of this class to the contact-surfaces c and c2; but since the electrical contact between these is maintained through a granulated conductor,wherein each grain or particle acts as a veritable electrodey with respect to those touching it on all sides,

the said surfaces in recognition of this fact are herein termed principal electrodes.

The dampening-spring cl2 is attached to a binding-post n at the upper edge of the faceplate, and to a corresponding screw-post y at its lower edge is fastened a ribbon or strip of metal foil or a similar light conductor @whose other end is bound between the shoulder or washer 7L and the diaphragm. This serves to secure a good circuit connection between the circuit-conductor L2 and the front contactelectrode e, while the requisite connection between the other circuit-wire L and the back electrode e2 may be made through the substance of the metal box c, to which the said wire L may be soldered, as shown, near the screw @c or wherever convenient. y

Transmitters of this class wherein the entire variable-resistance medium composed of the two principal electrodes and the granular carbon is contained in a chamber supported by the diaphragm alone, so that the whole chamber and its contents are shaken by the vibrations of the said diaphragm, have heretofore been strongly subject to the disadvantage of packing, resulting in diminished efficiency, because the entire tendency of such vibrations has inevitably been to shake the irregularly-shaped granulations to the bottom of the case. Instruments embodying the im- 'and back electrodes both mounted thereon,

the former being rigidly, and the latter elastically attached thereto; with a variable-resistance medium composed of substantially spherical or rounded carbon gran ules or particles, held between and in constant contact with the said electrodes; substantially as specified.

2. In a telephone-transmitter, the combination with the vibratory diaphragm, a case or chamber elastically attached to the said diaphragm and wholly supported thereby, an d two electrodes having adjacent contact-sur faces,inclosed in said case, one beingmounted directly on the diaphragm and the other on the back of the case; with a variable-resistance medium constituted of spherical or rounded particles of granulated carbon held between the said electrodes, within the said chamber; substantially as set forth.

3. The combination in a telephone-transmitter, with a diaphragm carrying both electrodes, one mounted directly thereon, and the other through an interposed elastic arm or plate; of a mass of granular carbon held between and in contact with the said electrodes to constitute a variable-resistance medium,

the grains or particles of carbon being spherical or rounded in form; substantially as set forth.

4. In a transmitting-telephone of the granular-carbon type, the combination with the diaphragm, of a case or chamber containing the electrodes, supported on the said diaphragm, and provided with a spring-back forming or carrying one of the said electrodes, the other being attached directly to the diaphragm,and a mass of rounded or substantially spherical carbon granules or particles held between the said electrodes within the said case 3 substantially as described.

5. In a transmitting-telephone of the granular-carbon type, the combination of the diaphragm, a resilient or elastic disk or plate secured centrally thereto, a containing case or chamber supported on the spring edges of the said plate and closed thereby, and a variable-resistance medium contained within the said chamber and consisting of a front electrode directly secured to the diaphragm,

IOO

602,174 I y a a complementary electrode carried upon the two subscribing Witnesses,` this 17th day of rear Wall of said chamber, and spherical 0I' August, 1897.

rounded carbon granulations held between the said electrodes; substantially as specified HERBERT E SHREEVE' 5 herein. Witnesses:

In testimony whereof I have signed my Y GEO. WILLIS PIERCE,

name t0 this specification, in chel presence of JOSEPH A. GATELY. 

